This invention relates to a semiconductor device washing apparatus and a method of washing the semiconductor device after a Chemical Mechanical Polishing (CMP) process.
Conventionally, irregularities are often formed on a surface of a semiconductor device having a laminate structure in a step of manufacturing the semiconductor device. The surface having the irregularities is flattened by the use of the known CMP (Chemical Mechanical Polishing) process.
This polishing process is generally carried out by using solution containing dense polishing particles (for example, silica particles, alumina particles) during the CPM process. These particles must be almost completely removed from a wafer surface after the CMP process to keep reliability of an electronic device and a desired cleaning degree of a manufacture line.
In particular, when a hydrophobic film, such as, a silicon nitride film and a polysilicon film, is polished, it is difficult to remove particles which are left on the hydrophobic surface in comparison with a hydrophilic surface. Therefore, a washing method of effectively removing the particles has been required.
A brush scrub method using a sheet-fed type spin washing apparatus is generally used as the method of removing the particles which are left on the wafer after the CMP process.
For example, the spin washing apparatus includes a roll blush 12, an exhaust nozzle 13, a chemical liquid tank 15, and a pure water exhaust nozzle 14, as illustrated in FIG. 1.
In this event, the roll brush 12 removes particles which are left on a wafer 11. In the exhaust nozzle 13, an exhaust hole is opposite to the wafer 11. Further, chemical liquid is contained in the chemical liquid tank 15. The chemical liquid is injected or sprayed from the exhaust hole towards or onto the wafer 11. Moreover, pure water is injected or sprayed from an exhaust hole of the pure water exhaust nozzle 14 towards or onto the wafer 11.
In the above-mentioned spin washing apparatus, the roll brush 12 is contacted with the wafer 11. The washing water is supplied from the chemical liquid tank 15 towards the wafer 11 through the exhaust nozzle 13.
Under this circumstance, the wafer 11 is washed by pure water which is injected from the pure water exhaust nozzle 14 on the condition that the wafer 11 and the roll brush 12 are rotated.
In this case, dilution ammonia solution (I. J. Malik et al.: MRS. Symp. Proc. Vol. 386, p.109 (1995)) or dilution hydrofluoric acid solution is used as the washing water other than the pure water. However, these solutions are not effective for washing the above-mentioned hydrophobic surface.
In contrast, a report has been made about an example in which hydrophobic property is improved to enhance the removing effect (or performance) by adding detergent during the CMP process and the subsequent washing process in the 57th prof. (p. 637, 8p-L-7) of [The Japan Society of Applied Physics]. Herein, it is to be noted that a main component of the washing solution may be uncertain in the above-mentioned report.
Further, disclosure has been made about a conventional example for obtaining a hydrophilic surface by adding alcohol liquid during the CMP process in Japanese Unexamined Patent Publication (JP-A) No. Hei. 9-277172.
However, the ammonia solution or the dilution hydrofluoric acid solution does not have capability for obtaining the hydrophilic surface. Consequently, it is not sufficiently effective to wash the hydrophobic surface.
On the other hand, although the ammonia water containing the detergent is effective, there is the following problem. Namely, it is easy that high-polymer organic substance constituting the detergent is left on the wafer after the washing process. Consequently, a washing step for removing the organic substance further becomes necessary.
Further, if a proper liquid wasting process is not performed for the detergent, the detergent gives an adverse effect for the environment. In consequence, it is necessary to prepare an expensive processing facility to carry out the proper process.
With respect to the example for adding the alcohol during the CMP process, the alcohol serves as a first washing liquid in a polishing apparatus for performing the CMP process. However, the alcohol does not serve as a final washing liquid for the subsequent step of depositing a film.
In general, the washing process in the polishing apparatus accompanies with contaminants inside the apparatus. Consequently, high cleaning washing can not be performed. As a result, an additional polishing apparatus is required to be arranged independently of the subsequent washing apparatus.
Further, when the hydrophobic surface, such as, the silicon nitride film and the polysilicon film, is exposed after the CPM process, it is difficult to remove the particles which are left on the hydrohobic surface as compared to the hydrophilic surface.
Therefore, a washing method for effectively removing the particles has been required.
It is therefore an object of this invention to provide a semiconductor device washing apparatus which is capable of improving removing performance of polishing particles.
It is another object of this invention to provide a semiconductor device washing apparatus in which particles almost does not remain on a wafer after a CMP process.
It is further object of this invention to provide a semiconductor device washing apparatus which is capable of readily processing wasting liquid.
According to this invention, a semiconductor device washing apparatus washes a surface of a semiconductor wafer after a chemical mechanical polishing process is performed for the surface.
Under this circumstance, a roll brush is placed on the surface of the semiconductor wafer so as to contact with the surface.
Further, a first chemical liquid tank contains first chemical liquid. A first exhaust nozzle sprays the first chemical liquid onto the surface of the semiconductor wafer.
Moreover, a second chemical liquid tank contains second chemical liquid. A second exhaust nozzle sprays the second chemical liquid onto the surface of the semiconductor wafer.
With such a structure, the first chemical liquid and the second chemical liquid are splayed onto the surface of the semiconductor wafer on the condition that the roll brush and the semiconductor wafer are rotated.
In this condition, polishing particles are left on the surface of the semiconductor wafer after the chemical mechanical polishing process. The roll brush removes the polishing particles from the surface of the semiconductor wafer.
In this case, the first exhaust nozzle has a first exhaust hole while the second exhaust nozzle has a second exhaust hole. Each of the first exhaust hole and the second exhaust hole is opposite to the surface of the semiconductor wafer. The first chemical liquid is sprayed onto the surface via the first exhaust hole while the second chemical liquid is sprayed onto the surface via the second exhaust hole.
In this event, the first chemical liquid comprises ammonia liquid while the second chemical liquid comprises alcohol liquid.
The ammonia liquid preferably comprises lower alcohol. In this event, the lower alcohol may be at least one selected from the group consisting of ethanol, methanol, and isopropyl alcohol.
Herein, the surface of the semiconductor wafer is hydrophobic. The hydrophobic surface is changed into a hydrophilic surface by the use of the alcohol liquid. In this event, the hydrophobic surface is changed into the hydrophilic surface in order to enhance removing performance of the polishing particles which are left on the semiconductor surface. The hydrophobic surface may comprise a surface in which a silicon nitride film or a polysilicon film is exposed.
Thus, the hydrophobic wafer surface is changed into the hydrophilic surface by adding the alcohol liquid, as mentioned before. Thereby, the removing performance of the particles is largely improved.
Further, the alcohol liquid is consisted of low molecular as compared to the detergent. Consequently, it is difficult that the particles are left on the wafer after the CMP process. Moreover, the alcohol liquid can be readily wasted in comparison with the detergent.
Moreover, this invention is effective for the wafer having the exposed surface which readily becomes hydrophobic, such as, the silicon nitride film and the polysilicon film after the CMP process. Under this condition, the polishing particles, which are left on the wafer, can be effectively removed.
Consequently, reliability of the semiconductor device can be enhanced. Further, cross contamination of the manufacturing line can be effectively suppressed. As a result, the manufacturing yield can be improved.
Moreover, the substance, such as, the detergent is not used in this invention. This is because it is difficult to waste the detergent. In consequence, the environment is not destroyed, and cost for wasting washing liquid can be largely reduced.